Yes but if you make a rule and someone in the class openly defies the rule, how can you keep that person in the classroom setting that horrible example? You tell them to give you their cell phone, they say no, you just go on about your class because you know you will flunk them in the end? No make sense.
Since the parents are ultimately responsible and pay for the cellphone....perhaps a fee for disruption (say $100 for the first episode, $1000 for the second) would get their attention. Either they’d correct her real quick or help to support the school in various financial ways.